Shallower depth is more about quads. Greater depth, below parallel, more about glutes and hamstrings.
A wider stance allows you to go deeper. So the stance width you choose depends on what you want to work. If you only care about quads, go narrow and shallow; if you want an arse, go wide and deep.
High bar is more comfortable and balanced for a narrow stance shallow squat, and low bar for a wider stance squat.
But in the end it's up to you, it's your body. Most of my clients have underdeveloped glutes and hamstrings, and are quad-dominant with poor core strength. So I give them low-bar wide stance squats. Or rather, I work them up to it - some can't manage the depth to begin with, they just collapse.